The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Energy generated by burning fossil fuel is converted into kinetic energy to drive a vehicle. Exhaust gas is generated in a combustion process of the fossil fuel, and harmful materials of the exhaust gas are purified. After that, the exhaust gas is exhausted into the atmosphere through an exhaust pipe.
An exhaust system of a vehicle may include a three-way catalyst for purifying harmful materials contained in exhaust gas. Recently, technology for mounting an additional catalytic converter in addition to a three-way catalyst has been under development.
Even though the additional catalytic converter is mounted on the exhaust pipe, it is difficult to remove harmful materials contained in the exhaust gas until a temperature of the exhaust gas reaches a light-off temperature of the catalyst in a case of cold starting where the temperature of the exhaust gas is very low. Particularly, a material such as a hydrocarbon is largely generated at initial starting, but hydrocarbons largely generated at the initial starting are not appropriately purified at the catalytic converter.
FIG. 4 is a graph illustrating a change in hydrocarbon concentration according to a conventional method of purifying exhaust gas.
As shown in FIG. 4, in a case where a hydrocarbon trap is used, hydrocarbons which cannot be purified at initial starting are inhibited from being exhausted to the exterior of the vehicle. However, since the hydrocarbons adsorbed in the hydrocarbon trap are started to be released before the temperature of the exhaust gas reaches a light-off temperature of a catalyst, purifying efficiency of the exhaust gas may be deteriorated.